1. Field of the Invention
The invention concerns an apparatus for defending against a missile attacking a craft with a thermal-optronic housing head for target tracking, wherein the optronic seeking or homing head of the missile to be defended against can operate in the range of the electromagnetic radiation spectrum from the ultraviolet to infrared.
2. Discussion of the Prior Art
It is therefore known (see the journal PM, Issue 7/1988, pages 48 to 57, in particular paragraph 2 in the right-hand column on page 50) for the homing head of an attacking air target missile to be blinded or diverted by the discharge of very bright and hot light bodies (so-called flares) from the threatened craft. Modem missile target tracking apparatuses however are already provided with sensors for distinguishing between flares and targets, for example by virtue of target contour image processing. They can therefore scarcely still be deflected by punctiform heat sources. That also applies in a corresponding fashion in relation to light-up ray sources for the irritation of UV-homing heads (see German patent specification No 41 07 533).
It is known from German laid-open application (DE-OS) No 36 23 808 for a high-energy laser beam to be held on a target point, once it has been detected, by way of a tracking regulator and an adaptive optical system for optimisation of the energy distribution over the beam cross-section, even when the target moves or when the reflection thereof, which is utilised for the tracking regulation effect, decreases, by virtue of the desired destruction of the equipment at the target point. Such a system appears to be well-suited for stationary or at any event land-bound lasers in terms of use against aircraft and large missiles; in order however to repel an attack by missiles against sea vessels or even aircraft, it would not be realistic to fit such systems for example to transport airplanes which have to be brought into use quickly for humanitarian purposes or for supplying crisis reaction forces and which are then required to fly over militarily unknown territory from which they can be put at extreme risk by partisans or rebels equipped with modern small-calibre air defense missiles.
In consideration of those factors, the present invention is based on the technical object of providing an effective defense apparatus with which potentially endangered craft can be readily subsequently fitted in order to fend off the threat of missiles controlled by a seeking or homing head.
In accordance with the invention that object is essentially attained in that the defense apparatus includes the craft being equipped with a laser source whose laser beam can be directed by way of the tracking optical system of a target tracking system as a defensive beam onto the approaching missile in order to put its housing head out of operation, depending upon the respective situation in terms of proximity, disturbing pulses, overloading or destruction.
In accordance with that construction, the craft to be protected is fitted with a comparatively compact laser source whose laser beam or beams is oriented by way of a panoramic-search warning sensor with a wide field of view coarsely in the direction of the threat and is then directed by the tracking optical means of an also passive target tracking system with a substantially narrower characteristic on to the dome, which already heats up due to friction, of the fast attacking guided missile. Because of the small diameter of the portable missile which is typically equipped with an infrared homing head, the risk of the target tracking system losing the attacker again with the defense laser beam is slight as when still at a medium distance the diameter of the guided missile is markedly smaller than the cross-section of the defense beam.
The thermal homing head detector is damaged or blinded by intensity modulation of the defense beam from a pulsed laser source or ( upon closer proximity ) by overloading, and thereby its target tracking regulating loop is put out of operation. Comparatively low levels of energy density in the defense beam are required for that purpose, if the wavelength thereof lies in the useful band of the homing head detector. Higher levels of energy density, as occur when the situation involves closer proximity, can even result in thermal destruction of the homing head, even when using non-thermal detectors in guided missiles of larger calibre, particularly when using very short pulses in the nanosecond range.
The use of a continuous-wave or pulse laser with a high pulse rate, with a comparatively low power level, for a search and illumination beam additionally affords the advantage of a quasi-stationary regulator action in regard to the actuation of an adaptive optical system comprising a wave front detector in order in addition to optimise the focussing of a higher-energy pulsed beam in the spectrally closely adjacent wavelength range over the same mirror plate topography for compensating for atmospheric disturbances in terms of propagation. That combination of active and auxiliary beams also makes it possible for the active beam to be pivoted slightly by way of an additional deflection unit relative to the track glint of the illumination beam and thus to direct it on to a location which is thermally more sensitive but which affords poorer reflection on the homing head of the missile to be defended against. That point can be determined by way of a video camera used as a track sensor. Locking on to the small-area target before a powerful clutter background and thereafter target tracking is enhanced if the camera is scanned on to the reflex pulse from the missile to be defended against, by way of a kind of aperture shutter (which can be embodied by the suitably short-term actuation of an image amplifier), so that the pulsed energy of the defense laser beam serves at the same time as stroboscopic illumination for emphasising the target point out of the ambient clutter.
The defense apparatus according to the invention can be installed to operate in an autarchic fashion in respect of energy in a narrow container which is suspended as an external load on the craft to be protected (for example under an aircraft). That makes it possible for the container to be suspended as required for example on various aircraft.